This invention relates to non-tacky sealant compositions based on a mercaptan-terminated liquid polymer. In accordance with another aspect, this invention relates to sealant compositions comprising liquid mercaptan-terminated polymers prepared from at least one of a mercapto acid and a mercapto acid ester and a primary hydroxy-terminated polyol. In accordance with another aspect, this invention relates to liquid mercaptan-terminated polymers prepared from at least one of a mercapto acid and a mercapto acid ester and a polyoxypropylene glycol end-capped with ethylene oxide prior to esterification to give primary hydroxy-terminated groups. In accordance with a further aspect, this invention relates to a process of preparing said mercaptan-terminated polymer from a mercapto acid and/or a mercapto acid ester and an ethylene oxide end-capped polyoxypropylene glycol. In accordance with another aspect, this invention relates to non-tacky sealant compositions comprising said mercaptan-terminated liquid polymer, non-elastomeric materials and a curing agent.
Poly(oxyalkylene)-polyester-poly(sulfide)-polythiols are broadly known as shown by U.S. Pat. No. 3,817,936. In one embodiment, this reference prepares the polymer by esterifying a mixture of mercaptocarboxylic and thiodicarboxylic acids with a polyoxypropylene glycol having on the average 2.5 pendant hydroxyl groups per molecule. Another method of preparing said polythiols is reported in U.S. Pat. No. 4,113,707 wherein, in one specific embodiment, a mixture of an alkyl mercaptocarboxylate and a dithiobis(alkylcarboxylate), and polythiobis(alkylcarboxylate) is transesterified with a polyoxypropylene glycol having on the average 2.5 pendant hydroxyl groups per molecule. These materials are quite useful in applications such as sealants. The compositions are normally liquid and can be easily cured with conventional curing agents such as sulfur, or lead peroxide to give a weather resistant flexible cured sealant. However, the cured sealant compositions have an initial surface tack that increases dirt, dust and other foreign matter pick-up. Although this initial surface tack diminishes with time and exposure to water, ultraviolet light and other environmental conditions, it is still desirable to have an elastomeric mercaptan-based sealant composition without initial surface tack. This invention is, therefore, an improvement in the sealant composition described broadly in U.S. Pat. Nos. 3,817,936, 4,113,707 and other poly(oxyalkylene)-polyester-poly(sulfide)-polythiols related inventions.
Accordingly, an object of this invention is to provide sealants based on poly(oxyalkylene)-polyester-poly(sulfide)-polythiol polymers.
Another object of this invention is to provide poly(oxyalkylene)-polyester-poly(sulfide)-polythiols which are curable to sealants having improved properties.
Another object of this invention is to provide cured non-tacky sealant compositions.
Other aspects, objects and the several advantages of this invention will be apparent to those skilled in the art upon a study of this disclosure and the appended claims.